SH7727 datasheet(166/1109 Pages) RENESAS

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Section 2 CPU

Rev. 5.00 Dec 12, 2005 page 94 of 1034

REJ09B0254-0500

Table 2.33 DC Bit Update Definitions

CS [2:0]

Condition Mode

Description

000Carry or borrow

mode

The DC bit is set if an ALU arithmetic operation generates a carry

or borrow, and is cleared otherwise.

When a PSHA or PSHL shift instruction is executed, the last bit

data shifted out is copied into the DC bit.

When an ALU logical operation is executed, the DC bit is always

cleared.

001Negative value

mode

When an ALU or shift (PSHA) arithmetic operation is executed,

the MSB of the result, including the guard bits, is copied into the

DC bit.

When an ALU or shift (PSHL) logical operation is executed, the

MSB of the result, excluding the guard bits, is copied into the DC

bit.

010Zero value mode

The DC bit is set if the result of an ALU or shift operation is all-

zeros, and is cleared otherwise.

011Overflow mode

The DC bit is set if the result of an ALU or shift (PSHA) arithmetic

operation exceeds the destination register range, excluding the

guard bits, and is cleared otherwise.

When an ALU or shift (PSHL) logical operation is executed, the

DC bit is always cleared.

100Signed greater-than

mode

This mode is similar to signed greater-or-equal mode, but DC is

cleared if the result is all-zeros.

DC = ~{(negative value ^ over-range) | zero value};

In case of arithmetic operation

DC = 0; In case of logical operation

101Signed greater-or-

equal mode

If the result of an ALU or shift (PSHA) arithmetic operation

exceeds the destination register range, including the guard bits

(“over-range”), the definition is the same as in negative value

mode. If the result is not over-range, the definition is the opposite

of that in negative value mode.

When an ALU or shift (PSHL) logical operation is executed, the

DC bit is always cleared.

DC = ~(negative value ^ over-range);

In case of arithmetic operation

DC = 0; In case of logical operation

110Reserved

111Reserved

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